Electrical burglar alarm system



B. MENKIN 2,617,868

ELECTRICAL BURGLAR ALARM SYSTEM Nov. 11, 1952 Filed March 2, 1951 2SHEETSSHEET l INVENTOR. BURNETT MENKIN wry/M ATTORNEY.

Nov. 11, 1952 MENKlN ELECTRICAL BURGLAR ALARM SYSTEM 2 SHEETS--SHEET 2Filed March 2, 1951 INVENTOR.

BURNETT MENKIN ATTORNEY.

n 3 3 R f ,l 9 6 2 ms u m m n D I G 7 7 H O G 6 8 m w m 6 v J 4 A 6 0 6Patented Nov. 11, 1952 UNITED STATES PATENT OFFICE ELECTRICAL BUBGLARALARM SYSTEM Burnett Menkin, New York, N. Y.

Application March 2, 1951, Serial No. 213,649

Claims. 1

This invention relates to improvements in electrical burglar alarmsystems, and it relates more particularly to a signal or alarm systemresponsive, when in operative or set condition, to the movement ofdoors, windows, or the like, having protective switches associatedtherewith.

The principal object of the present invention is to provide anelectrical burglar alarm system of the type which may be finally set bythe closing of a door, whereby the last person to leave a protectedbuilding may place the system in operative condition by the mere closingof the exit door as he leaves the building.

A further object of the present invention is to provide a burglar alarmsystem of the character aforesaid, having improved means for renderingthe various alarm circuits operative by the final closing of the exitdoor.

A further object of the invention is to provide a burglar alarm systemof the character aforesaid having a key operated look by means of whichthe system may be rendered inert during the normal occupancy and use ofthe protected building, having improved means whereby the system may bepartially set preliminarily to the final closing of the door which willcomplete the setting thereof.

A further object of the invention is to provide a burglar alarm systemof the character aforesaid, having improved means for insuring theretention of the relay armature in the position for maintaining thealarm circuit open during the preliminary setting of the system.

A further object of the invention is to provide improved means in aburglar alarm system of the character aforesaid for indicating faults inthe various circuits.

The nature and characteristic features of the invention will be morereadily understood from the following description, taken in connectionwith the accompanying drawings forming part hereof, in which:

Figure l is a diagrammatic view of a burglar alarm system embodying thefeatures of the present invention, the same being shown with the partsin the inert condition, such as the same would be during the periods ofnormal use of the protected building, when it is necessary to use thevarious doors and other protected openings;

Fig. 2 is a View similar to Fig. 1, but illustrating the system in itsoperative or set condition;

Fig. 3 is a plan view illustrating a modified form of the invention, ofa more simplified char acter, but lacking certain of the desirablefeatures shown in Figs. 1 and 2.

Fig. 4 is a view partly in perspective illustrating certain of the dooroperated switches used in the system; and

Fig. 5 is a view illustrating a modified form of a key operated settinglock employed in the system.

It should, of course, be understood that the description and drawingsherein are illustrative merely, and that various modifications andchanges may be made in the arrangements shown without departing from thespirit of the invention.

Referring now more particularly to Figs. 1 and 2 of the drawings,certain of the parts are mounted on a panel, the outline of which isindicated by dotted lines at It]. The panel is provided with a series ofbinding posts, A, B, C, D, E, F, and G, for convenience in wiring.

H is the battery or other source of direct current. The terminals of thebattery H are respectively connected to the binding posts D and E bylines H and I2.

Mounted on the panel is a relay J, one end of the coil [3 of which isconnected by line l4 to binding post A, and the other end of the coil13.

of which is connected by line IE to the binding post B. The winding ofthe coil 13 of the relay J is of high resistance, of the order of about2000 ohms. The armature IQ of the relay J is connected by line IT to thebinding post E to which one of the terminals of the battery H isconnected.

For the proper operation of the system it is necessary that the armaturel6, when in its released or free position will not be attracted to thepole of the relay coil even when the same is energized, but for theinitial setting thereof said armature must be assisted to themagnetically held position, closer to the pole of the relay magnet, in amanner to be presently described. The armature iii of the relay J isadapted, when released, to engage a contact screw [8 mounted in abracket !9. The bracket I9 is connected by line 20 to one of theterminals of a buzzer 21. The other terminal of the buzzer 2| isconnected by line 22 to the binding post G.

The winding of the coils of the buzzer 2| is such that the buzzer willnot ordinarily be actuated by the normal amount of current passingthrough the line, but the same will be actuated under certain conditionsof faults in the line, whereby an increased amount of current will bepermitted to flow.

A shunt line 23 extends from line 20 to line;

22 and is provided with a normally open switch 24 included therein.

The terminals of the buzzer 2! are connected to a resistance unit 25.

Mounted on the panel adjacent the relay J is a switch lock K, the bolt30 of which is extended when the system is inert and retracted when thesystem is placed in the operative or set position.

The outer end of the bolt 30 of the lock K engages a spring arm 3| whichcarries a cylinder 32. The cylinder 32 serves to support a plunger 33,the outer end of which is adapted under tension of a spring 34 tocontact the armature E of the relay J for the purpose of positioning thearmature l5 close to the pole 35 of the relay magnet l3 when the bolt 30of the switch lock K is extended so as thereafter to hold the armaturewhile the relay coil remains energized.

The purpose of the above described device is to insure that the armaturel6 of the relay J will be held within the range of the magneticattraction of the pole 35 of the relay J for a sufiicient period, as thebolt 30 of the switch lock is being retracted, until the main circuit isestablished, by the switching arrangement to be presently described, toenergize the coil l3 of the relay J.

Adjacent the spring arm 3| which is controlled by the switch lock is aspring arm 35 insulated from spring arm 31 and the contact 3'! at itsfree end which is adapted, when the bolt 36 of the switch lock K isretracted, to engage the contact 38 carried at the end of another springarm 39 arranged adjacent thereto.

The spring arm 36 is connected by line it to the binding post D, whichis connected to one of the terminals of battery H. The other spring arm39 is connected by line 4! to binding post F.

One of the principal novel features of the present invention is the dooroperated switch M which is used as the means for effecting the finalsetting of the alarm system to operative condition. Said door operatedswitch M is shown in the lower part of each of wiring diagrams of Figs.1 and 2, and isalso illustrated in further detail in Fig. 3 of thedrawings, the same comprising a plate member 50 adapted to be secured toa fixed portion of the building, such as the header of the door frame.Said plate 50 serves as a support for a cylinder 5| in which a sleevemember 52 is slidablymounted. A spring 53 within the cylinder 5| impelsthe sleeve member 52 to its outermost position as shown in Fig. 1 of thedrawings.

In the sleeve member 52 a plunger 54 is mounted which is connected by arod 55 to a contact disc 56 at the inner end thereof.

The contact disc 56 is adapted, when the door is open, to contact aspring arm 51 on one side, and to be seated in a notch 58 in a springarm 59 on the other side of the supporting cylinder 5!. The spring arm59 also has an additional notch 60 in which the contact disc 56 isseated when the door is in its closed position.

The spring arm 51 is of such length that, when the door is in the closedposition, the contact disc 56 will be separated therefrom, and nocurrent will then pass through the spring arm 57. However, there isassociated with the spring arm 57 another spring arm 6| which isadapted, when the door is closed, to be engaged by a contact screw 52carried by a bracket 63 secured to a portion of the door.

The door 0 is also provided with another bracket member or arm 64 whichis adapted, as the door is closed, to first engage the sleeve member 52,and thereafter to engage the plunger 54 '4 to push the contact disc 56to its innermost position when the door is closed.

The bracket member or arm 54 is connected to the bracket 53 by line 67which may comprise a strip of metal foil disposed adjacent the edge of aglass panel, when such is used as a part of the door 0.

The spring arm M which is adapted to be contacted by the screw 52 isconnected by line 68 to the binding post A. The spring arm 59 which hasthe notches engaged by the contact disc 56 is connected by line 59,which may be one of the wires of the house circuit, to the binding postG.

A line is is connected at one end to the binding post B and at its otherend to binding post C. Included in the lines 59 and 15 are the normallyclosed detector switches i! which may be used in connection with thepanels, doors and windows in the protected building, so as to break thecircuit when any of the said switches are opened by reason of theopening of a door or window or other opening with which said switch isassociated.

A line 12 run from the binding post F to one terminal of the alarm bellR and the return line l3 runs from the other terminal of the alarm bellR to binding post G.

A resistance unit 14 is connected across the terminals of the alarm bellR.

A shunt line i9 having a normally closed switch 8! included therein runsfrom the line til which connects the spring arm 39 to the binding postF. Said shunt line 79 is connected to one of the terminals of the buzzer80, the other terminal of which is connected by line 82 to binding postG. The coils of the buzzer 85 are also of low ohm winding, and thisbuzzer will be actuated whenever the alarm circuit is closed. Aresistance unit 83, is connected across the terminals of the buzzer 80.

A line 8Q extends from binding post C to one of the terminals of abuzzer 65 the other terminal of which is connected by line 86 to bindingpost E. The coils of the buzzer 35 are however of a higher ohm windingthan those of the buzzers 2i and 8E].

The winding of the coils of the buzzer 85 is such that the buzzer willnot ordinarily be actuated by the normal amount of current passingthrough the line, but will be actuated under certain conditions offaults in the line whereby an increased amount of current will bepermitted to flow.

A shunt line 87 extends from one of the terminals of the buzzer 85 andhas included therein a normally open switch 88. The terminals of thebuzzer 85 are also connected to a resistance unit 89.

The operation of the system and patricularly the novel portions thereofmay now be explained.

When the system is out of use as, for example, in the day time, duringthe usual and ordinary use of the protected building, the lock K isactuated, causing the bolt 38 of the lock to extend and bear against thespring arm 3! permitting the spring arm 35 to move so that the contact31 thereof will be separated from the contact 38 which is carried by thespring arm 39.

As the spring arm 35 is connected by line 36 to binding post D, andthence by line H to one of the terminals of the battery H, it will beapparent that when the lock is thus operated, the supply of current fromthe battery will be cut off by the separation of the contacts 37 and 38,and the entire system will thus be rendered inert.

It-will also be apparent that when the bolt 30 of the lock K isprojecting outward, as above, the spring actuated plunger 33 carried byspring arm 3| will i-mpinge. against the armature [6 of the relay Jthereby breaking the circuit which comes by line I! to armature i6 andthence to contact screw I 8, thereby preventing the current from passingthrough buzzer 2|, or its resistance unit 25, or the switch 24 when saidswitch is closed.

One end of the coil l3 of the relay J is connected by line H throughbinding post A, and line 68 to the spring arm 5! of the door switch M,and thence through contact disc 56 to spring arm 59, to house line 69which is connected to binding post G.

The other end of the relay coil is connected through line [5 to bindingpost B and through house line 18 to binding post C, and thence throughthe lines by which buzzer 85 is connected to binding post E. However,when the door 0 is closed, the circuit will be established from bindingpost A through line 68 and spring arm 61' of the door switch M, saidspring arm 6! being adapted to be engaged by the contact screw 62carried by the door, thus connecting the door panel line 67 into thecircuit when the door is closed, it being noted that as the door isclosed, the bracket 64 will first push the sleeve 52 inwardly until thebracket 64 encounters the plug 55 pushing the same inwardly to cause thecontact disc 55 to disengage from the notch 58 of the spring arm 59, andthereafter be seated in the notch 69 of said spring arm. The circuit maythus be initially established when the door is open, and thereaftermaintained when the door is closed.

When it is desired to put the system into operation the door is firstopened to the position indicated in Fig. 1 of the drawings, after whichthe lock K is operated to cause the bolt 39 there-- of to be retracted.

The retraction of the bolt 39 results in the makingof the main circuitthrough the contacts 3'! and 38 so that in setting the system, theoperator will first cause the bolt 39 of the lock to be retracted andthen as he passes on through the door the closing thereof will cause thedetector circuit to be maintained and the line on the door panel, forthe protection thereof, will be cut into said circuit.

However, the relay J will be energized prior to the making of the maincircuit through the contacts 31 and 38, and will thus hold the armatureIS in the position shown in Fig. 1 of the drawings, whereby the circuitthrough the line i! coming from binding post E to line l2 will bemaintained open, and the alarm bell circuit thus rendered inert untilthe main circuit is broken either through one of the switches II, ineither of the house line 59 or m, or by the opening of said circuitthrough the breaking of the line 93' which protects the door panel, orthe cutting of any of the wires in said circuit.

Should the door 0 be improperly opened while the system is in theoperative or set condition, the contact disc 56 will be retained in thenotch 68 of the spring arm 59 until after the contact screw 52 has leftthe spring arm SI, and in this manner the detector circuit will beopened, and the coil E3 of the relay will thereby be de-energized, thuscausing the alarm bell R to ring by reason of the armature l6 contactingthe screw 19 and thus establishing the alarm circuit.

In Fig. 3 of the drawings there is shown a simplified, arrangement ofthe circuits which,

however, will not have all the advantageous features of the arrangementshown in Figs. 1 and 2 of the drawings. As there shown, the sameutilizes a panel 318 similar to the panel [0 of the other form andbinding posts A B C D E and F In this arrangement the battery H isconnected, similarly as in the other arrangement, to the binding posts Dand E The relay J has a coil 313 connected at one end by line 3M tobinding post A The other end of the coil 3l3 is connected by line 3l5 tobinding post B The binding post A is connected by line 368 whichconstitutes one of the detector or house lines to the door settingswitch M which is of the same construction as the switch M in Fig. 1 ofthe drawings. The other end of switch M is connected by line 369 tobinding post F The lines 368 and 369 are each provided with detectorswitches 31! at the doors, windows and other openings of the building tobe protected.

The house line 310 is connected at one end to binding post B and at itsother end to binding post C and also being provided with detectorswitches 37!.

Binding post E is connected by line 312 to one of the terminals of thealarm bell R the other terminal of the alarm bell is connected by line373 to binding post F In this form of the invention, binding post 0 isconnected by line 384 to one of the terminals of the buzzer 385, theother terminal of which is connected by line 386 to binding post E Theterminals of the buzzer 3-85 are also connected by a shunt line 381,having a switch 388 included therein.

The relay J is also provided with an armature 3 i 6 which is connectedby line 3|! to binding post D The armature 3| 6 is adapted, when freedfrom the attraction to the pole 335 of the relay coil 3|3, to contactwith the terminal 3! of the line 329. The terminal 3l8 of line 320 may,if desired, be like the contact screw [8 shown in Fig. 1 of thedrawings.

The line 320 is connected to one of the terminals of a buzzer 32!, theother terminal of which is connected by line 323 to binding post F Ashunt 323 extends from line 320 to line 322, having a switch 324included therein, adapted when the switch is closed to bypass thecurrent around the buzzer 32L The line 379 extends from binding post Eto one of the terminals of a buzzer 389, and switch 38l included in saidline.

The buzzer 389 has a resistance unit 389 connected in shunt across theterminals thereof, the buzzer 32I has a resistance unit 325 connected inshunt across the terminals thereof and the buzzer 38!] has a resistanceunit 383 connected in shunt across the terminals thereof.

There is also provided a setting lock K the bolt 33B of which is adaptedwhen extended to hold the armature 316 of the relay out of engagementwith the contact 3l8 thereof.

The operation of the arrangement shown in Fig. 3 of the drawings issubstantially similar to that shown in Fig. l with the exception of theomission of the additional feature shown in Fig. 1 of the automaticopening of the circuit by the separation of the contacts 37 and 38,carried by the spring arms 36 and 39 respectively.

In Fig. 5 of the drawings there is shown a novel form of lock switchwhich is so constructed and arranged that the circuit will be maintainedthrough the relay coil during the unlocking period. As there shown, thesame comprises the provision of a spring member 9| so mounted to beactuated by the inner end of the key when the'same is inserted in thelock K or K as the case may be. Said spring member 9! is connected byline 92 to line so which is connected to spring member 36, and a portionof the lock housing is connected by line as to line M which is connectedto spring arm 39.

I claim:

1. An electrical burglar alarm comprising a source of electrical energy,a primary circuit in which the same in included, a detector circuithaving detector switches included therein, an alarm circuit having analarm device included therein, a relay the coil of which is included inthe detector circuit, an armature controlled by said relay adapted toclose the alarm circuit when the relay coil is de-energized, a switchlock having a movable. member adapted to hold the armature of the relayin circuit breaking position, a switch associated with said movable lockmember adapted to open the primary circuit when the movable lock memberis in position to hold the armature of the relay in its position tobreak the alarm circuit, means associated with the movable lock memberfor holding the armature in said alarm circuit breaking position untilthe switch in the primary circuit is closed and the relay coil therebyenergized, a signal device in the alarm circuit and a signal device inthe detector circuit, each of said signal devices in the alarm anddetector circuits having a resistance unit in a shunt circuit wherebysaid signal device will be actuated in the event of faults in said alarmand detector circuits causing a variance of the current flow throughsaid signal devices.

2. An electrical burglar alarm comprising a source of electrical energy,a primary circuit in which the same is included, a detector circuithaving detector switches included therein, an alarm circuit having analarm device included therein, a relay the coil of which is included inthe detector circuit, an armature controlled by said relay adapted toclose the alarm circuit when the relay coil is de-energized, a switchlock having a movable member adapted to hold'the armature of the relayin circuit breaking position, a switch associated with said movable lockmember adapted to open the primary circuit when the movable lock memberis in position to hold the armature of the relay in its position tobreak the alarm circuit, means associated with the movable lock memberfor holding the armature in said alarm circuit breaking position untilthe switch in the primary circuit is closed and the relay coil therebyenergized, and a door operated switch in the detector circuit adapted,when the door is closed, after the relay coil is energized, to completethe setting of the system, and thereafter to open the detector circuitin the event the door is opened.

3. An electrical burglar alarm comprising a source of electrical energy,a primary circuit in which the same is included, a detector circuithaving detector switches included therein, an alarm circuit having analarm device included therein, a relay the coil of which is included inthe detector circuit, an armature controlled by said relay adapted toclose the alarm circuit when the relay coil is de-energized, a

switch lock having a movable member adapted to hold the armature of therelay in circuit breaking position, a switch associated with saidmovable lock member adapted to open the primary circuit when the movablelock member is in position to hold the armature of the relay in itsposition to break the alarm circuit, means associated with the movablelock member for holding the armature in said alarm circuit breakingposition until the switch in the primary circuit is closed and the relaycoil thereby energized, and a door operated switch in the detectorcircuit adapted when the door is closed, after the relay coil isenergized, to complete the setting of the system, and thereafter to openthe detector circuit in the event the door is opened, said switch alsobeing constructed and arranged to cut in a door protective circuit whenthe door is closed.

4. An electrical burglar alarm comprising a source of electrical energy,a primary circuit in which the same is included, a detector circuithaving detector switches included therein, an alarm circuit having analarm device included therein, a relay the coil of which is included inthe detector circuit, an armature controlled by said relay adapted toclose the alarm circuit when the relay coil is de-energized, a switchlock having a movable member adapted to hold the armature of the relayin circuit breaking position, a switch associated with said movable lockmember adapted to open the primary circuit when the movable lock memberis in position to hold the armature of the relay in its position tobreak the alarm circuit, means associated. with the movable lock memberfor holding the armature in said alarm circuit breaking position untilthe switch in the primary circuit is closed and the relay coil therebyenergized, a signal device in the alarm circuit and a signal device inthe etector circuit, each of said signal devices in the alarm anddetector circuits having a resistance unit in a shunt circuit wherebysaid signal device will be actuated in the event of faults in saidcircuits causing a variance of the current flow through said signaldevices, and a door operated switch in the detector circuit adapted whenthe door is closed, after the relay coil is energized, to complete thesetting of the system, and thereafter to open the detector circuit inthe event the door is opened.

5..An electrical burglar alarm comprising a source of electrical energy,a primary circuit in which the same is included, a detector circuithaving detector switches included therein, an alarm circuit having analarm device included therein, a relay the coil of which is included inthe detector circuit, an armature controlled by said relay adapted toclose the alarm circuit when the relay coil is ale-energized, a switchlock having a movable member adapted to hold the armature of the relayin circuit breaking position, a switch associated with said movable lockmember adapted to open the primary circuit when the movable lock memberis in position to hold the armature of the relay in its position tobreak the alarm circuit, means associated with the movable lock memberfor holding the armature in said alarm circuit breaking position untilthe switch in the primary circuit is closed and the relay coil therebyenergized, a signal device in the primary circuit adapted to be actuatedwhen the alarm device is actuated, a signal device in the alarm circuitand a signal device in the detector circuit, each of said signal devicesin the alarm and de-t tector circuits having a resistance unit in ashunt circuit whereby said signal device will be actuated in the eventof faults in said alarm and detector:

circuits causing a variance of the current flow through said signaldevices, and a door operated switch in the detector circuit adapted whenthe door is closed, after the relay coil is energized, to complete thesetting of the system, and thereafter to open the detector circuit inthe event that the door is opened.

6. An electrical burglar alarm comprising a source of electrical energy,a primary circuit in which the same is included, a detector circuithaving detector switches included therein, an alarm circuit having analarm device included therein, a relay the coil of which is included inthe detector circuit, an armature controlled by said relay adapted toclose the alarm circuit when the relay coil is de-energized, a switchlock having a movable member adapted to hold the armature of the relayin circuit breaking position, a switch associated with said movable lockmember adapted to open the primary circuit when the movable lock memberis in position to hold the armature of the relay in its position tobreak the alarm circuit, means associated with the movable lock memberfor holding the armature in said alarm circuit breaking position untilthe switch in the primary circuit is closed and the relay coil therebyenergized, a signal device in the primary circuit adapted to be actuatedwhen the alarm device is actuated, a signal device in the alarm circuitand a signal device in the detector circuit, each of said signal devicesin the alarm and detector circuits having a resistance unit in a shuntcircuit whereby said signal device will be actuated in the event offaults in said alarm and detector circuits causing a variance of thecurrent flow through said signal devices, and a door operated switch inthe detector circuit adapted when the door is closed, after the relaycoil is energized, to complete the setting of the system, and thereafterto open the detector circuit in the event the door is opened, saidswitch also being constructed and arranged to cut in a door protectivecircuit when the door is closed.

'7. An electrical burglar alarm comprising a source of electricalenergy, a primary circuit in which the same is included, a detectorcircuit having detector switches included therein, an alarm circuithaving an alarm device included therein, a relay the coil of which isincluded in the detector circuit, an armature controlled by said relayadapted to close the alarm circuit when the relay coil is de-energized,a switch lock having a movable member adapted to hold the armature ofthe relay in circuit breaking position, a

switch associated with said movable lock member adapted to open theprimary circuit when the movable lock member is in position to hold thearmature of the relay in its position to break the alarm circuit, meansassociated with the movable lock member for holding the armature in saidalarm circuit breaking position for energizing the relay coil priortoand until the switch in the primary circuit is closed, said meanscomprising a shunt circuit around the switch in the primary circuit andmeans included in said shunt circuit to close the same upon insertion ofa key in the switch lock.

8. An electrical burglar alarm comprising a source of electrical energy,a primary circuit in which the same is included, a detector circuithaving detector switches included therein, an alarm circuit having analarm device included therein, a relay the coil of which is included inthe detector circuit, an armature controlled by said relay adapted toclose the alarm circuit when the relay coil is de-energized, a switchlock having a movable member adapted to hold the armature of the relayin circuit breaking position, a switch associated with said movable lockmember adapted to open the primary circuit when the movable lock memberis in position to hold the armature of the relay in its position tobreak the alarm circuit, means associated with the movable lock memberfor holding the armature in said alarm circuit breaking position forenergizing the relay coil prior to and until the switch in the primarycircuit is closed, said means comprising a key controlled shunt circuitaround the switch in the primary circuit.

9. In an electrical burglar alarm system including a detector circuithaving detector switches therein, a door operated switch in saiddetector circuit adapted to complete the setting of the system, saidswitch comprising a pair of spring arms, a contact member adapted tocontact both of said arms and thereby maintain the circuit when the dooris open, said contact member being movable to a position to break thecontact with one of said arms when the door is closed, an auxiliarycontact arm electrically connected to said last mentioned arm adapted tobe engaged when the door is closed by a contact member carried by thedoor, another member carried by the door adapted to actuate the movablecontact member when the door is closed and to establish an electricalconnection therewith, an electrical connection between the memberscarried by the door, and means for restraining the movement of themovable contact member when the door is opened until the contact membercarried by the door is separated from the auxiliary contact arm.

10. In an electrical burglar alarm system including a detector circuithaving detector switches therein, a door operated switch in saiddetector circuit adapted to complete the setting of the system, saidswitch comprising a pair of spring arms, a contact member adapted tocontact both of said arms and thereby maintain the circuit when the dooris open, said contact member being movable to a position to break thecontact with one of said arms when the door is closed, an auxiliarycontact arm electrically connected to said last mentioned arm adapted tobe engaged when the door is closed by a contact member carried by thedoor, another member carried by the door adapted to actuate the movablecontact member when the door is closed and to establish an electricalconnection therewith, an electrical connection between the memberscarried by the door including a protective line positioned marginally ona panel of the door, and means for restraining the movement of themovable cont-act member when the door is opened until the contact membercarried by the door is separated from the auxiliary contact arm.

BURNETT MENKIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,365,693 Hess Jan. 18, 19211,758,523 Kertz May 13, 1930 2,243,804 Howton May 2'7, 1941

